The entire disclosure of Japanese Patent Application No. 2007-337472 filed on Dec. 27, 2007 is expressly incorporated by reference herein.
1. Technical Field
The present invention relates to a liquid jet apparatus arranged to form predetermined characters and images by emitting microscopic droplets of liquids from a plurality of nozzles to form the microscopic particles (dots) thereof on a medium.
2. Related Art
Incidentally, in liquid jet printing apparatuses using the liquid jet apparatus, a drive signal amplified by a power amplifying circuit is applied to an actuator such as a piezoelectric element to emit a jet of a liquid from a nozzle, and if the drive signal is amplified by an analog power amplifier such as a linearly driven push-pull coupled transistor, a substantial power loss is caused, and a large heat sink for radiation is required. Therefore, according to JP-A-2005-329710, the drive signal is amplified using a digital power amplifier, thereby reducing the power loss, and eliminating the heat sink.
In the case of power-amplifying the drive signal using the digital power amplifier, it is a common practice to execute pulse modulation on a drive waveform signal acting as the basis for the drive signal, and to execute digital power amplification on the modulated signal. Incidentally, in the case of performing high-quality and high-speed printing with a one-pass operation using a line head printing apparatus, the time required for printing one dot is extremely short. For example, if a piezoelectric element is used as the actuator, it is required to pull in the liquid in the nozzle and then push it out to eject a jet of the liquid within the short time required for printing a dot, which requires a drive voltage signal with an accurate trapezoidal waveform. Since the drive waveform signal is as precise as the drive signal, in order for executing accurate pulse modulation on the precise drive waveform signal, it is required to always keeping the timing of the pulse modulation such as the phase of the triangular wave signal in pulse-width modulation in a constant condition with respect to the drive waveform signal.
Therefore, it is possible to adopt a method of resetting the timing of the pulse modulation such as the triangular wave signal itself using a reset signal forming the basis of actuator drive timing necessary for the case of performing printing with a line head printing apparatus, in other words, a reset signal forming the basis of drive signal generation timing.
However, by simply resetting the triangular wave signal in sync with the reset signal, the duty ratio of the modulated signal in the vicinity of the reset signal problematically varies, which causes a problem that the accurate drive signal cannot be obtained.